a) Field of the Invention
The present invention relates to an automotive sunshade panel formed from a hollow panel having a two-dimensional or three-dimensional curved surface conforming to a bent curved surface in the form of the top of an automobile, and to a method of manufacturing such an automotive sunshade panel.
b) Description of the Prior Art
To manufacture a bent panel having a large radius of curvature such as an interior side sunshade panel for an automotive sunroof, in the prior art techniques, the pressed body obtained from press work using dies and reinforcing members such as ribs were assembled together by bonding means including spot welding, riveting, adhesion, etc, since typical roll-based bending work often gave birth to spring back resulting in a dimensional instability. Japanese Patent Laid-open Pub. No. 96-90080 discloses a method of manufacturing through bulging a bent panel having inflations serving as reinforcing ribs from an aluminum Roll-Bond panel stock. For the manufacture of the bent panel, in the above invention, use was made of a forming machine provided with a forming surface having a curved surface of a radius of curvature to be formed. A planar stock is disposed on the forming machine. A punch holder of the forming machine is then lowered to chuck the peripheries of the planar stock. With the peripheries being chucked, the planar stock is finally brought into abutment against the forming surface. In the case of press forming an automotive sunshade panel by means of dies as in those conventional methods, however, a multiplicity of dies corresponding to various types of vehicles are required, and hence relatively small-lot products result uneconomically in a relative increase of cost used up by the dies.
Furthermore, the invention described in the above publication uses an aluminum Roll-Bond panel as stock. This stock tends to bring about a decrease in the gauge direction with a forming force during the press forming, as well as deficiencies such as collapse of the inflated portions. Although fabrics are typically laminated to the automotive sunshade panel, they must be laminated to the curved surface after pressing since lamination before pressing may possibly allow the fabrics to peel off under the action of lubricant used in the pressing process. This resulted in increased number of working steps and was costly.
Typical stock for the automotive sunshade panel can be a thermoset resin sheet, a steel sheet, or an aluminum sheet, with a recent attention paid to the aluminum sheet (including aluminum alloy sheet) in terms of its lightweight and recyclability. In view of rigidity and cost-saving, the aluminum sheet has a gauge of the order of 0.8 to 1.0 mmt for pressing process. On the contrary, it has been hitherto known to bend the stock by use of twin rolls consisting of a metal roll and a resin roll as shown in FIG. 2. In the case of bending the aluminum sheet of the order of 0.8 to 1.0 mmt in gauge by using the above metal/resin roll pairs serving as rigid/elastic roll pairs, it would be possible to perform bending with a relatively small radius of curvature, but impossible to bend the stock having a relatively large radium of curvature of the order of 2500 to 10000 mm due to the influence of the spring back. Thus, the reinforcing members such as ribs become indispensable and the configuration is unstable, leaving unsolved the problems including dependence on the press forming and fabric lamination after press forming.